Donkeys are being beaten, brutally whipped around racecourses and forced to drink alcohol at a Mexican festival that claims to champion the helpless animals, MailOnline can reveal.

The humiliating main event of the 51st Annual Donkey Festival in Otumba, an hour from Mexico City, is the costume competition, which on Sunday was won by a drunken donkey dressed as a Smurf.

The heavily scarred animal took home £500 for its owners who painted him blue, force fed him five litres of beer and fitted a 15kg fibreglass toadstool on his back to keep him from running away.

'We put a lot of thought into the costume, and spray-painting him helped to cover up the scars on his flanks', said Antonio Oldera, 52, whose animal beat off competition from 'Fireman Donkey', 'Uber Donkey' and 'Aztec Pyramid Donkey'.

'The spray paint won't be out of his hair for another two weeks, but his most pressing issue will be tomorrow's hangover,' he told MailOnline as a delighted crowd of 5,000 Mexicans cheered his animal to victory.

The town of Otumba, just ten minutes from the ancient Mexican pyramids of Teotihuacan, holds the bizarre festival on the first Sunday of May every year.

It attracts more than 5,000 visitors to the 'Donkeydrome', where costume competitions, races and even donkey polo events are held.

'This entire town loves donkeys,' said Juan Carlos Chavez, standing beside his scarred animal, 'We rely entirely on them for our livelihoods, and we want to honour them every year with this party.'

Despite its popularity, animal rights groups have condemned the event, claiming donkeys are tortured for the crowd's amusement.

'It's a disgusting practice which sick people take pleasure from,' said Leonora Esquivel, the founder of Mexico's leading animal rights group AnimaNaturalis.

She told MailOnline: 'The use of animals for entertainment has been banned in circuses in Mexico. So why should a town's annual festival that charges people entry be any different?'

But Mexico State congresswoman Cristina Sanchez refused to see it as animal cruelty and told MailOnline: 'If anything it's a day off work for the animals.'

Sanchez, who was guest of honour at the annual event, added: 'It's a great event that represents the local mind-set of hard work.'

Five of the 24 donkeys competing in the costume competition were dressed as Donald Trump. One of them carried a banner promising to 'build a wall between Mexico City and Otumba'.

'Even the donkey is embarrassed to be dressed as Trump,' said Carla Chavez, 24, who told said she dreads the idea of the real estate magnate as president of the US.

She added: 'It's our way of ridiculing a man we see as very disrespectful to Mexico.'

Another entrant dressed up both his pig and donkey up as Donald Trump and claimed while the donkey was an imposter, the pig was the real candidate for president.

'They make a lot of noise, and can be very aggressive when they get scared,' said the reigning Miss Otumba Katy Gernantellez, 17, as she posed beside Mariachi Donkey, 'But the older ones are used to it by this point.'

Ignacio Alvarez, 30, whose Tequila donkey was eliminated in the costume competition's first round, said he gave alcohol to his animal to stop it from getting scared when it reached the procession.

'He scares very easily,' he told MailOnline, as he jumped on top of the scarred animal's back, making it bray and kick.

He added: 'But a few sips of pulque (a viscous alcoholic drink made from maguey) keeps him calm.'

One of the most popular snacks sold at the festival is donkey meat, which is heavily seasoned with chilli and other spices to compensate for its tough texture and acrid taste.

'We eat donkey all year round in this town,' said one seller, who was also offering grilled grasshoppers to his customers, 'It's a chance for our visitors to have a real taste of life in Otumba.'

Following Smurf Donkey's lap of honour in front of the cheering crowd, the proceedings moved onto the donkey races where six animals were to complete a single lap of the 'Donkeydrome' track.

Fully grown men acted as jockeys, each carrying a bamboo stick which they used to slash at their donkeys' necks and hinds in a cruel attempt to make them gallop faster.

Alejandro Hernandez from Mexico City said: 'It's a great event, I don't know of any other donkey festival in the whole world. It's fun to watch the things the locals do with their animals.'

Away from the 5,000-seater 'Donkeydrome', other events saw farmers glue five-foot fibreglass horns onto bulls, merry-go-rounds with real horses and even a python that tourists could wrap around their necks.

In an animal market elsewhere in Otumba, pigs, peacocks, chinchillas, game cocks and even weasels were sold to the general public.

As the afternoon progressed, the crowds delighted in gallons of pulque, beer mixed with tomato juice and a beverage made from fermented pineapple rind.

As night fell, the dancing crowd took the place of the livestock in the dusty centre of the Donkeydrome.

'We're all much more drunk than the animals by the time we're finished', said Donkey Festival spokesman Carlos Mares. 'Man or beast, everyone has a good time in Otumba'.

Read the original story on the Daily Mail